Thin films of silicon dioxide, silicon nitride, and mixtures thereof are some of the most commonly used materials in semiconductor manufacturing due to their excellent dielectric properties. In the manufacturing of silicon based semiconductor devices, these materials can be used as gate insulation, diffusion masks, side wall spacers, hard mask, anti-reflection coating, passivation and encapsulation, etc. Silicon-based films are also becoming increasingly important for passivation of other compound semiconductor devices.
When silicon-based films are used in conjunction with wet etch process, an important and routine production process for the fabrication of silicon integrated circuits, the wet etch rate of silicon dioxide films are critical to many applications. In some cases (e.g., when the silicon dioxide is used side wall), the etch rate in HF solution needs to extremely slow since a too fast and aggressive action on the material would make it difficult to control the undercut and the line-width. A slower, controllable etch rate is desirable for a better manufacturing process, supporting higher yield of semiconductor devices. In some other cases where silicon-based films are used as etch stops, hard masks, or passivation layers, it is desirable for the material to be extremely resistant to wet etching.
Existing approaches of forming silicon-based films that have low etch rate in HF solution are    (1) depositing the films at higher temperatures to reduce the defects such as porosity or hydrogen concentration in the film, or    (2) adding other precursors to the deposition process in addition to silicon or nitrogen during the deposition process to bring in additional elements to modify film properties.
Since higher temperatures may not always be desirable, and the use of multiple precursors can add complexity to the process, alternatives to controlling film properties are desired.
Prior art in this field includes US Published Patent Application U.S.2010/0120262 and U.S. patent application Ser. No. 12/772,518 filed May 3, 2010.